Hi Colin,
It is worth getting the $50 deal - you can easily do a clean install with the upgrade media - even if you do not already have the qualifying version of Windows to start with.
You don't to install a different o/s - 7 installer will recognize your current Vista install as qualifying.
Another way is to start the 7 install - it asks to see a qualifying version of Windows - pop a 2000 or XP or Vista dvd in the drive - it will accept that.
Another way is to boot 7 dvd - select Custom install - do not enter product key - highlight Edition you have purchased - tick the box saying I have selected the edition I purchased - install to partition of your choice . ( That will run as a 30 day trial )
While booted into that fresh 7 install, put the 7 dvd in the drive - run setup - select Upgrade install - this time enter product key.
If you actually want to do an upgrade install ( rather than a clean install) over your Vista Ult - afraid not - you will need to do a clean install.
Vista to Windows 7 upgrades:
- No upgrade options for Windows Vista Starter (SP1, SP2), not even to Windows 7 Starter;
- Windows Vista Home Basic (SP1, SP2) 32-bit (x86) and 64-bit (x64) can be upgraded to Windows 7 Home Basic, Home Premium and Ultimate 32-bit (x86) and 64-bit (x64);
- Windows Vista Home Premium (SP1, SP2) 32-bit (x86) and 64-bit (x64) can be upgraded to Windows 7 Home Premium and Ultimate 32-bit (x86) and 64-bit (x64);
- Windows Vista Business (SP1, SP2) 32-bit (x86) and 64-bit (x64) can be upgraded to Windows 7 Professional, Enterprise and Ultimate 32-bit (x86) and 64-bit (x64);
- Windows Vista Enterprise (SP1, SP2) 32-bit (x86) and 64-bit (x64) can be upgraded to Windows 7 Enterprise 32-bit (x86) and 64-bit (x64);
- Windows Vista Ultimate (SP1, SP2) 32-bit (x86) and 64-bit (x64) can be upgraded to Windows 7 Ultimate 32-bit (x86) and 64-bit (x64);
- No upgrade options for Windows Vista Home Basic N (SP1, SP2), not even to Windows 7 N or E;
- No upgrade options for Windows Vista Business N (SP1, SP2), not even to Windows 7 N or E.